Common name
American Eel
Scientific name
Anguilla rostrata (Lesueur)
Description
American eels have a snake-like body, with a narrow, pointed head. Their lower jaw usually protrudes beyond the upper jaw; the gape extends to below or behind the eye. They also have vertical gill slits on the sides of their necks. American eels have no pelvic fins, and their dorsal, anal and caudal fins are one continuous fin that comes to a rounded tip at the end. To a certain degree, eels can change their colour to match their surroundings. They also change colour with developmental stage.
The larval stage (see Figure above, and Ontario Ministry of Natural Resources) is called a leptocephalus (which means leaf-shaped) and it is transparent, absorbs most of its nutrients directly through its skin, and drift at sea for about 1 year. The leptocephali then develop into transparent glass eels that have prominent black eyes. Glass eels enter estuaries and start to migrate upstream towards freshwater habitats as elvers which are characterized by darker colouring, from gray to greenish brown. The next stage, the yellow eel, is the sub-adult form that lives in freshwater; color ranges from yellow to olive-brown. The yellow eel stage lasts from 5 to 20 years! Sexually mature adults, silver eels, are dark brown and gray dorsally, with a silver to white ventral side. Females outgrow males so an eel measured to be greater than 45cm is likely a female and one measured greater than 50-60 cm is almost certainly female. The sexually mature silver eels migrate to the Sargasso Sea to spawn and then die.
Geographic range
The American eel is commonly found in estuaries and freshwater tributaries along the eastern Atlantic Ocean from Greenland and Iceland to the northern coast of South America. They occupy the most extensive range (over 10,000 km of continental coastline between latitudes ~ 7 and 55o N) of any fish in the Americas.
Habitat
This species is more common near the sea in estuarine waters rather than inland streams and lakes. They live most of their lives in fresh or brackish water but because of their life cycle, they travel across a wide range of salinities and habitats. They can be found anywhere from the deep ocean in the Sargasso Sea when breeding to continental shelves as larvae, to estuaries and freshwater streams in later life stages. As adults, American eels typically swim near the bottom in search of food. The species prefers to hunt at night and resides in crevices or other shelter from the light during the day, often times burying themselves in the substrate, whether mud, sand or gravel. Adult eels have been observed foraging during the daytime in seagrass habitats in local estuaries.
Diet
Eels will feed on amphibians, crustaceans, insects, fish and basically whatever comes their way. They are also known to scavenge dead animals. They are the prey of other animals in their ecosystem such as larger fishes including haddock (Melanogrammus aeglefinus) and spiny dogfish (Squalus acanthias) and diving birds such as double-crested cormorants (Phalacrocorax auritus)
Additional websites
- American eel fact sheet - Unversity of Michigan Museum of Zoology: Animal Diversity Web
- Status of Fishery Resources off the Northeastern U.S. Northeast Fisheries Science Center – National Oceanic and Atmospheric Administration
- American eel – Fishes of the Gulf of Maine
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